Cationic laminar compounds and their production and use as stabilizers for halogen containing plastics

ABSTRACT

A process for the production of cationic layer compounds wherein layer compounds corresponding to general formula (I): 
     
         --[E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x 
    
      ](A n- ) a .qH 2  O--                            (I) 
     in which 
     E is a monovalent cation from the group consisting of alkali metals, 
     e is a number of 0 to 2, 
     Z is a divalent metal cation, 
     z is a number of 0 to 6, 
     D is a trivalent metal cation, 
     d is a number of 0 to 3, 
     V is a tetravalent metal cation, 
     v is a number of 0 to 1, 
     (A n- ) is an acid anion having the charge n- where n is an integer of 1 to 3, 
     q is a number of 1 to 10, 
     with the proviso that x&gt;a and e+2z+3d+4v=x+na, are subjected to alkali-induced ripening in aqueous medium wherein the alkali metal hydroxide content of said aqueous medium is adjusted to a value in the 1- to 6-molar range, the crystallization temperature is adjusted to a value in the range from 60° C. to 100° C., and the crystallization time is adjusted to a value in the range from 2.5 to 50 hours.

BACKGROUND OF THE INVENTION

1. Field of the Invention

This invention relates to special cationic layer compounds of thehydrotalcite type, to a process for their production and to their use asstabilizers for halogen-containing plastics.

It is known that halogen-containing plastics or molding compoundsproduced from them tend to degrade or decompose on exposure to heat orhigh-energy radiation, for example ultraviolet light. To counteractthis, they are normally treated with heavy metal compounds based, forexample, on lead, barium and/or cadmium. For reasons of factory hygiene,however, there is a need to replace these thoroughly effectivestabilizers by less health-damaging materials. Possible alternativestabilizers to the heavy metal compounds are, for example calcium andzinc soaps, but unfortunately they do not perform as well as the heavymetal compounds mentioned above so that co-stabilizers have to be usedin order to enhance their stabilizing effect.

2. Discussion of Related Art

German patent DE-C-30 19 632 (Kyowa Chemical Ind.) describes the use ofhydrotalcites for inhibiting the thermal or ultraviolet degradation ofhalogen-containing thermoplastic resins. This patent specificationdiscloses test results which show that, when readily commerciallyavailable hydrotal-cites are incorporated, for example, in vinylchloride resins, they accelerate the dechlorination of the resins onheating or even cause decomposition, blackening or foaming of theresins. In addition, it was found that these hydrotalcites show poordispersibility in the resins and adversely affect the rheologicalproperties of the resins during molding and also the appearance of themolded products obtained. These test results are attributed to the smallcrystal size of the usual hydrotalcites and to the large specific BETsurface of at least about 50 m² /g and the coverage of the hydrotalciteparticles with water. Accordingly, it is proposed in German patentDE-C-30 19 632 to use hydrotalcites which have a large crystal size anda specific BET surface of no larger than 30 m² /g and which mayoptionally be coated with an anionic surfactant, such as sodiumstearate.

European patent application EP-A-189 899 (Kyowa Chemical Ind.) alsodescribes resin compositions containing hydrotalcites having specificBET surfaces below 30 m² /g. It is known from this European patentapplication that the hydrotalcites can be modified with higher fattyacid esters, anionic surfactants and coupling agents of the silane ortitanium type in order to improve the compatibility of the hydrotalcitewith the resins. According to cited European patent application EP-A-189 899, the hydrotalcites are said to be modified by mechanical mixingwith the modifying agents in pure or dissolved form.

DEC-33 06 822 (Giulini Chemie) teaches that hydrotalcites with theformula [Mg₆ Al₂ (OH)₁₂ ](CO₃)₂.xH₂ O (with x≧2) are obtained byreaction of aluminium hydroxide with magnesium hydroxide or magnesiumoxide in the presence of basic magnesium carbonate as carbonate iondonor at a temperature of 50 to 100° C. and subsequent spray drying fromthe suspension. The aluminium hydroxide is used in particular in theform of "active" aluminium hydroxide.

U.S. Pat. No. 4,656,156 (Aluminium Company of America) describes aprocess for producing hydrotalcite in which the aluminate liquor of theBayer process is used as the aluminium component. The Bayer liquor isreacted with "active" magnesium oxide which can be obtained, forexample, by calcining magnesium carbonate. This process can only beeconomically used in places where the Bayer liquor itself accumulatesbecause otherwise relatively large quantities of water would again haveto be transported.

DE-A-15 92 126 (Kyowa Chemical Ind.) describes the production ofhydrotalcites from different starting materials, for example from asuspension of solid aluminium hydroxide, solid magnesium hydroxide andsodium hydrogen carbonate. The reactions are carried out in batches andthe products are separated from the water phase by filtration orcentrifugation and washed before they are dried.

According to DE-C-44 25 266 (Metaligesellschaft AG), the familiarsubject of stabilizing halogen-containing plastics is outlined asfollows: halogen-containing thermoplastic resins, such as polyvinylchloride, are converted during processing (melt forming) into polyenestructures with elimination of hydrogen chloride (HCl). The polymerbecomes discolored. In order to improve thermal stability, metalcarboxylates ("metal soaps") are normally incorporated in the resin asstabilizers. However, since the incorporation of such substances as solestabilizers can lead to so-called metal burning in the event ofrelatively prolonged melt forming processes, resulting in blackening ofthe polymer, it is standard practice to add a co-stabilizer. Typicalco-stabilizers are, for example, polyols, organic phosphorous acidesters or epoxy compounds. According to the teaching of DE-C-44 25 266,special lithium-ontaining layer lattice compounds can be used forstabilizing PVC in particular. In addition, DE-A-44 25 275(Metaligesell-schaft AG) also teaches the use of similar Li-containinglayer lattice compounds for stabilizing halogen-containing plastics.

DESCRIPTION OF THE INVENTION

The problem addressed by the present invention was to providestabilizers for halogen-containing plastics which would be distinguishedby an improved action profile in relation to the prior art. Inparticular, they would have the following properties:

Compatibility with calcium and/or zinc compounds.

Dispersibility in halogen-containing plastics without adverselyaffecting their rheological properties.

Pronounced ability to effectively trap the decomposition products ofhalogen-containing plastics. This would mean above all improvedproperties in regard to their ability to absorb hydrogen chloride.

Improvement in the long-term stability of halogen-containing plastics,particularly PVC (polyvinyl chloride).

The present invention relates first to a process for the production ofcationic layer compounds in which layer compounds corresponding togeneral formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

in which

E is a monovalent cation from the group of alkali metals,

e is a number of 0 to 2,

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

V is a tetravalent metal cation,

v is a number of 0 to 1,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and e+2z+3d+4v=x+na, are subjected toalkali-induced ripening in aqueous medium. The alkali metal hydroxidecontent of the aqueous medium is adjusted to a value in the 1- to6-molar range, the ripening temperature is adjusted to a value in therange from 60 to 100° C. and the ripening time is adjusted to a value inthe range from 2.5 to 50 hours.

A particular advantage of the process according to the invention is thatit can be carried out in the absence of pressure in an open reactor.This is particularly economical from the point of view of processtechnology. In particular, it is pointed out in this connection that theprocess according to the invention does not require hydrothermalconditions (i.e. temperatures above 100° C. and pressures above 1atmosphere).

In one embodiment, layer compounds corresponding to general formula (I)where v=0 are used to carry out the process according to the invention.Accordingly, these layer compounds may be represented by the generalformula (I*):

    [E.sub.e Z.sub.z D.sub.d (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O(I*)

in which

E is a monovalent cation from the group of alkali metals,

e is a number of 0 to 2,

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and e+2z+3d=x+na.

In another embodiment, layer compounds corresponding to general formula(I) where e=0 are used to carry out the process according to theinvention. Accordingly, these layer compounds may be represented by thegeneral formula (I**):

    [Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O(I**)

in which

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

V is a tetravalent metal cation,

v is a number of 0 to 1,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and 2z+3d+4v=x+na.

In one preferred embodiment, layer compounds corresponding to generalformula (I) where e and v are both 0 are used to carry out the processaccording to the invention. Accordingly, these layer compounds may berepresented by the general formula (I***):

    [Z.sub.z D.sub.d (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O(I***)

in which

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and 2z+3d=x+na.

The layer compounds corresponding to formula (I***) are "raditional"hydrotalcites which have been known to the expert for some time. Ofthese hydrotalcites, those in which D is aluminium, d is the number 1and z is a number of 1 to 5 are preferred. These special hydrotalcitesare characterized by the general formula (I****):

    [Z.sub.z Al(OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O   (I****)

in which

Z is a divalent metal cation,

z is a number of 1 to 5,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3 and

q is a number of 1 to 10,

with the proviso that x>a and 2z+3=x+na.

The essence of the invention is that the lattice structure of cationiclayer compounds (I)--more particularly conventional hydrotalcitescorresponding to general formulae (I***) and (I****)--undergoes analkali-induced modification such that, on the one hand, thecrystallinity of the layer compound is improved and, on the other hand,the effect of the resulting layer compounds as co-stabilizers forhalogen-containing plastics is lastingly improved. The origin of thelayer compound (I) used is not critical. It may be of natural origin ormay be synthetically produced. In the case of synthetic layer compounds(I), it does not matter whether the compound is used as a solid orwhether it was prepared in situ immediately before the alkali-inducedripening and, hence, is present in the form of an aqueous suspension.

The ripening medium is a 1- to 6-molar aqueous alkali metal hydroxidesolution. However, 3- to 5-molar solutions are preferably used.Basically, the type of alkali metal hydroxide used to prepare theaqueous alkaline medium is not critical. However, sodium hydroxide isgenerally used.

The ripening temperature is a temperature in the range from 60 to 100°C. and preferably in the range from 70 to 90° C.

Basically, the ripening time is in the range from 2.5 to 100 hours. Ifit is below the lower limit of this range, the desired improvement inthe action spectrum of the layer compounds is not guaranteed. If itexceeds the upper limit mentioned, any further improvement in the actionspectnrun is very limited so that exceeding this upper limit isuneconomical. Preferred crystallization times are in the range from 10to 20 hours.

The cationic layer compounds (I) are compounds known per se of which thestructure and preparation are described, for example, by W. T. Reichlein Chemtec (January 1986), pages 58 to 63. The prototype of cationiclayer compounds is the mineral hydrotalcite [Mg₆ Al₂ (OH)₁₆ ](CO₃).4H₂O. Structurally, hydrotalcite derives from brucite [Mg(OH)₂ ]. Brucitecrystallizes in a layer structure with the metal ions in octahedralvacancies between two layers of hexagonally close-packed (OH⁻) ions.Only every second layer of the octahedral vacancies is occupied by metalions M so that layer packages (OH)--M--(OH) are formed. In brucite, theinterlayers are empty. In hydrotalcite, some of the Mg(II) ions--sayevery second to fifth--are statistically replaced by Al(III) ions.Overall, the layer package thus receives a positive charge. This chargeis equalized by anions which are present in the interlayers togetherwith readily removable water of crystallization. Scheme 1 belowdiagrammatically illustrates the layer structure of hydrotalcite:

    ______________________________________                                        Cationic layer OH.sub.-                                                          Mg.sup.2+  Al.sup.3+                                                          OH.sup.-                                                                     Interlayer (CO.sub.3).sup.2-  H.sub.2 O                                       Cationic layer OH.sub.-                                                        Mg.sup.2+  Al.sup.3+                                                          OH.sup.-                                                                   ______________________________________                                    

SCHEME 1

Hydrotalcites form powders with BET surfaces of up to about 150 m² /gwhich have a talcum-like feel. Two basic syntheses are known from theliterature. The first comprises treating aqueous solutions of thecorresponding metal salts with lye, the hydrotalcite formedprecipitating. The second synthesis starts out from water-insolublestarting compounds, such as metal oxides and hydroxides. The reactionsinvolved are heterogeneous reactions which are normally carried out inan autoclave.

As already mentioned, hydrotalcite is merely the prototype of cationiclayer compounds. However, the synthesis methods known from hydrotalciteare also generally used for the synthesis of cationic layer compounds.As known to the expert, these synthesis methods may be classified quitegenerally as hydrothermal syntheses. Hydrothermal synthesis in thenarrower sense is the synthesis of minerals from highly heated (>100°C./1 atm.) aqueous suspensions. Hydrothermal syntheses are generallycarried out in pressure vessels because the temperatures applied are farabove the boiling point of water and, in most cases, even above itscritical temperature (cf. Rompps Chemie-Lexikon, ⁷ 1973, p. 1539).

Cationic layer compounds (I) in which Z represents at least one divalentmetal ion selected from the group consisting of magnesium, calcium andzinc are preferred for the purposes of the invention. In a preferredembodiment, Z represents exactly one divalent metal ion from the groupmentioned, more particularly magnesium. Cationic layer compoundscorresponding to general formula I, in which A^(n-) represents an acidanion having a charge of (n-) selected from the group of anionsconsisting of carbonate, hydrogen carbonate, perchlorate, acetate,nitrate, tartrate, oxalate and iodide, preferably carbonate, are mostparticularly preferred. Where reference is made to at least one divalentmetal ion in the explanation of formula I above, it means that differentdivalent metal ions may also be present alongside one another in thecationic layer compound. The indices x, y and z and m may representwhole or broken numbers within the limits mentioned. Cationic layercompounds corresponding to general formula I, in which Z representsmagnesium and Al represents carbonate, are particularly advantageous.

Basically, the BET surface of the cationic layer compounds (I) to beused in accordance with the invention is not critical. However, layercompounds (I) with a BET surface above 50 m² /g are preferably used. Apreferred embodiment of the invention is characterized by the use oflayer compounds (I) with an average particle size of 20 to 50 μm.

Examples of suitable cationic layer compounds are synthetichydrotalcites which are also known as basic aluminium/magnesiumcarbonates and which are generally produced by the process described inDE-B-15 92 126 and by the processes described in DE-A-20 61 114 or DE-A29 05 256.

Suitable sources of divalent metal ions are their carbonates,hydroxocarbonates, hydroxides, oxides or their water-soluble salts, forexample nitrates, chlorides, sulfates or perchlorates. Sources ofdivalent metal ions which already contain the anion A^(n-) areparticularly preferred. In this case, there is no need to add anadditional source of these anions. For example, it is particularlypreferred to use at least part of the divalent metal ions as carbonatesor as hydroxocarbonates. If only the oxides or hydroxides are used asthe source of divalent metal ions, an additional source of the anionsA^(n-), for example in the form of alkali metal salts, has to be used.Alkali metal salts of carbonic acid and/or of oxo acids of halogens, forexample perchloric acid, are preferred and may be added to the reactionmixture in quantities of 1 to 100 mole-%, based on the aluminiumcontent. For example, sodium carbonate may be added to the reactionmixture.

Both fine-particle active aluminium(III) hydroxide in combination withsodium hydroxide and NaAlO₂ may be used as the aluminium source.Aluminium chloride, bromide, nitrate and sulfate may also be used.

The present invention also relates to cationic layer compoundsobtainable by subjecting layer compounds corresponding to generalformula (I)

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.31 ).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

in which

E is a monovalent cation from the group of alkali metals,

e is a number of 0 to 2,

Z is a divalent metal cation,

z is a number of 0to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

V is a tetravalent metal cation,

v is a number of 0 to 1,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and e+2z+3d+4v=x+na, to alkali-inducedripening in aqueous medium, the alkali metal hydroxide content of theaqueous medium being adjusted to a value in the 1- to 6-molar range, thecrystallization temperature being adjusted to a value in the range from60 to 100° C. and the crystallization time being adjusted to a value inthe range from 2.5 to 50 hours.

The present invention also relates to compositions for stabilizinghalogen-containing plastics against thermal or photochemical degradationcontaining cationic layer compounds obtainable by subjecting layercompounds corresponding to general formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x](A.sup.n-).sub.a.qH.sub.2 O                                                         (I)

in which

E is a monovalent cation from the group of alkali metals,

e is a number of 0 to 2,

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

V is a tetravalent metal cation,

v is a number of 0 to 1,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and e+2z+3d+4v=x+na, to alkali-inducedripening in aqueous medium, the alkali metal hydroxide content of theaqueous medium being adjusted to a value in the 1- to 6-molar range, thecrystallization temperature being adjusted to a value in the range from60 to 100° C. and the crystallization time being adjusted to a value inthe range from 2.5 to 50 hours.

The substances produced in accordance with the invention mayadvantageously be used as stabilizers for halogen-containingthermoplastic resins. Examples of such resins are PVC, polyvinylidenechloride, chlorinated or chlorosulfonated polyethylene, chlorinatedpolypropylene or chlorinated ethylene/vinyl acetate copolymers. Thecationic layer lattice compounds produced in accordance with theinvention are particularly suitable as stabilizers for resins of the PVCtype, i.e. on the one hand vinyl chloride homopolymers and, on the otherhand, copolymers of vinyl chloride with other monomers.

Accordingly, the present invention also relates to the use of cationiclayer compounds obtainable by subjecting layer compounds correspondingto general formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

in which

E is a monovalent cation from the group of alkali metals,

e is a number of 0 to 2,

Z is a divalent metal cation,

z is a number of 0 to 6,

D is a trivalent metal cation,

d is a number of 0 to 3,

V is a tetravalent metal cation,

v is a number of 0 to 1,

(A^(n-)) is an acid anion with the charge n- where n is an integer of 1to 3,

q is a number of 1 to 10,

with the proviso that x>a and e+2z +3d+4v=x+na, to alkali-inducedripening in aqueous medium, the alkali metal hydroxide content of theaqueous medium being adjusted to a value in the 1- to 6-molar range, thecrystallization temperature being adjusted to a value in the range from60 to 100° C. and the crystallization time being adjusted to a value inthe range from 2.5 to 50 hours, for stabilizing halogen-containingplastics against thermal or photochemical degradation.

The cationic layer compounds produced in accordance with the inventionare preferably used as co-stabilizers for halogen-containing plasticsstabilized with calcium and/or zinc salts of carboxylic acids containing6 to 22 carbon atoms. More particularly, the cationic layer compoundsproduced in accordance with the invention are used as co-stabilizers inpolyvinyl chloride. To this end, the cationic layer compounds are addedin quantities of 0.01 to 5 parts by weight and preferably 0.1 to 3 partsby weight per 100 parts by weight of synthetic resins disregarding anyorganic additives which may be present. In general, they aremechanically mixed with the plastics present in granular form beforemolding, for example by calendering and extrusion. Commercial zincand/or calcium salts of carboxylic acids containing 6 to 22 carbon atomsare incorporated as conventional stabilizers, generally at the same timeas the cationic layer compounds. Other conventional additives, such asthe heat stabilizers described in European patent application EP-A-189899, may of course also be used. The quantities in which the stabilizersand co-stabilizers are used may vary as required, with the proviso thatthe total quantity of stabilizer added is within the limits of 0.5 to 5parts by weight per 100 parts by weight of synthetic resin. Accordingly,the minimum quantity of cationic layer compound is at least 0.01% byweight.

The effect of zinc and/or calcium soaps as stabilizers forhalogen-containing plastics is enhanced by the use of the cationic layercompounds according to the invention. In addition, the cationic layercompounds as co-stabilizers may readily be incorporated in thehalogen-containing plastics without adversely affecting theirrheological properties.

If desired, the cationic layer compounds produced in accordance with theinvention may be subsequently modified with at least one liquid orlow-melting dispersing additive selected from compounds belonging togroups A) to F) identified below by intensive mixing at room temperature(15 or 25° C.) or at a temperature below the decomposition temperaturesof the cationic layer compounds and/or the additives, preferably below300° C. Additive groups A) to F) are:

A) polyols containing 3 to 30 carbon atoms and at least two hydroxylgroups,

B) esters of partly or completely epoxidized unsaturated carboxylicacids containing 6 to 22 carbon atoms,

C) full and partial esters of polyols containing 3 to 30 carbon atomsand 2 to 12 hydroxyl groups with carboxylic acids containing 6 to 22carbon atoms,

D) alkyl and aryl phosphites,

E) anions of saturated or unsaturated fatty acids containing 6 to 22carbon atoms,

F) polymers with a molecular weight of 500 to 50,000 which are solublein water with pH values above 8.

Suitable group A) additives are polyols containing at least two hydroxylgroups and a total of 3 to 30 carbon atoms. Examples of such polyols arediols containing 3 to 30 carbon atoms, such as butanediols, hexanediols,dodecanediols, and polyols, such as trimethylol propane,pentaerythritol, glycerol and technical oligomer mixtures thereof withaverage degrees of condensation of 2 to 10. Most particularly preferredgroup A) additives are polyols containing 3 to 30 carbon atoms of whichthe carbon skeleton bears at least one hydroxyl group or one etheroxygen every 3 carbon atoms, preferably glycerol and/or technicaloligoglycerol mixtures with average degrees of condensation of 2 to 10.The tris-(2-hydroxyethyl)-isocyanurate known as "THEIC" (EP-B 377 428)is also particularly suitable for use as such an additive.

The group B) additives are esters of partly or completely epoxidizedunsaturated carboxylic acids containing 6 to 22 carbon atoms. Suitableesters are esters of mono-, di- and/or trihydric alcohols which arecompletely esterified with epoxidized unsaturated carboxylic acidscontaining 6 to 22 carbon atoms, such as methyl, 2-ethylhexyl, ethyleneglycol, butanediol, neopentyl glycol, glycerol and/or trimethylolpropane esters of epoxidized lauroleic acid, palmitoleic acid, oleicacid, ricinoleic acid, linoleic acid and/or linolenic acid. Esters oftrihydric alcohols and completely epoxidized unsaturated carboxylicacids containing 12 to 22 carbon atoms are preferred, esters of glycerolwith completely epoxidized unsaturated carboxylic acids containing 12 to22 carbon atoms being particularly preferred. The carboxylic acidcomponent may be derived, for example, from palmitoleic acid, oleicacid, elaidic acid, petroselic acid, ricinoleic acid, linolenic acid,gadoleic acid or erucic acid. The unsaturated carboxylic acids areepoxidized by known methods. As usual in oleochemistry, the epoxidizedcarboxylic acid glycerides may also be the technical mixtures obtainedby epoxidation of natural unsaturated fats and oils. Epoxidized rapeseedoil, epoxidized unsaturated soybean oil and/or epoxidized sunflower oilfrom new plants is/are preferably used.

The group C) additives are full or partial esters which may be obtainedby the relevant methods of preparative organic chemistry, for example byacid-catalyzed reaction of polyols with carboxylic acids. The polyolcomponent may be selected from those already discussed in relation togroup A). Preferred acid components are aliphatic, saturated and/orunsaturated carboxylic acids containing 6 to 22 carbon atoms, such ascaproic acid, caprylic acid, capric acid, lauric acid, myristic acid,palmitic acid, palmitoleic acid, stearic acid, oleic acid, ricinoleicacid, linoleic acid, linolenic acid, behenic acid or erucic acid. Asusual in oleochemistry, the carboxylic acid component may even be atechnical mixture of the type accumulating in the pressure hydrolysis ofnatural fats and oils. Partial esters of glycerol and, in particular,technical oligoglycerol mixtures with average degrees of condensation of2 to 10 and saturated and/or unsaturated aliphatic carboxylic acidscontaining 6 to 22 carbon atoms are preferred.

Suitable group D) additives are alkyl and aryl phosphites, preferablythose corresponding to general formula (II): ##STR1## in which R¹, R²and R³ independently of one another represent an alkyl group containing1 to 18 carbon atoms or a phenyl group. Typical examples of group D)additives are tributyl phosphite, triphenyl phosphite, dimethyl phenylphosphite and/or dimethyl stearyl phosphite. Diphenyl decyl phosphite ispreferred.

Suitable group E) additives are anions of saturated or mono- orpolyunsaturated fatty acids containing 6 to 22 carbon atoms which may belinear or branched. Linear fatty acids are preferred by virtue of theireasier accessibility. Pure fatty acids, for example lauric acid,myristic acid, palmitic acid, stearic acid, lauroleic acid, myristoleicacid, palmitoleic acid, oleic acid, linoleic acid or linolenic acid, aresuitable. However, it is also economically attractive to use fatty acidmixtures of the type obtainable from the hydrolysis of natural oils andfats. It does not matter whether the fatty acids are used as such or inthe form of preferably water-soluble salts, for example sodium orpotassium salts. Since the reaction mixture is highly alkaline, thereaction product will contain the fatty acids in any event in the formof their anions.

Additives of group F) are polymers with an average (number average)molecular weight of 500 to 50,000 which are soluble in water with pHvalues above 8 and preferably with pH values of 9 to 12. In the presentcontext, "soluble" means that more than 0.01% by weight of the polymericadditives and preferably at least 0.1% by weight is dissolved completelyclearly, above all under the described conditions, in an aqueoussolution with a pH value of 10 adjusted with alkali metal hydroxides at20° C. In principle, any polymers known to the expert as pigmentdispersants (cf. Kirk-Othmer "Encyclopedia of Chemical Technology", Vol.7, 3rd Edition, 1979, pages 840-841 or Ullmann's "Encyclopedia ofIndustrial Chemistry", Vol. A8, 5th Edition, 1987, pages 586-601) may beused as polymeric additives providing they meet the solubility andmolecular weight requirements. Acrylic acid and methacrylic acidhomopolymers and copolymers, lignin sulfonates and trimer fatty acidsare preferred polymeric additives. Particularly suitable polymericadditives are those selected from the group of polymers of acrylic acidand methacrylic acid and copolymers thereof with unsaturated monomerscontaining sulfonic acid groups, unsaturated monomers containingphosphonic acid groups, unsaturated aliphatic carboxylic acidscontaining 3 to 5 carbon atoms, amides of unsaturated aliphaticcarboxylic acids containing 3 to 5 carbon atoms, unsaturated monomerscontaining amino groups and/or salts thereof, vinyl acetate, vinylchloride, acrylonitrile, vinylidene chloride, 1,3butadiene, styrene,alkyl styrenes containing 1 to 4 carbon atoms in the alkyl group.Examples of such polymeric additives are polyacrylic acid,polymethacrylic acid (acrylic acid and methacrylic acid and derivativesthereof are hereinafter referred to in short as (meth)acrylic acid orderivatives) and/or salts thereof, such as polysodium (meth)acrylate,copolymers of (meth)acrylic acid with maleic acid, maleic anhydride,styrene sulfonic acid, α-methyl styrene, 2-vinyl pyridine, 1-vinylimidazole, dimethyl aminopropyl (meth)-acrylamide,2-(meth)acrylamido-2-methyl propane sulfonic acid, (meth)acryl-amide,N-hydroxydimethyl (meth)acrylamide and/or salts thereof. Among thepolymeric additives, those which are predominantly anionic in character,i.e. which contain mostly acid groups either in free form or in the formof their salts, are most particularly preferred. Polymers of(meth)acrylic acid and copolymers thereof with styrene, alkyl styrenescontaining 1 to 4 carbon atoms in the alkyl group, styrene sulfonicacid, maleic acid andlor salts thereof, particularly sodium salts, andmaleic anhydride are particularly preferred. The polymeric additivespreferably have a molecular weight of 1,000 to 10,000. The polymericadditives may be produced by known methods, such as bulk or solutionpolymerization (cf. Ullmann's Encyclopadie der technischen Chemie, Vol.19, 4th Edition, pages 2-11, 1980). Processes for the production oflignin sulfonic acid and salts thereof are also described in Ullmann'sEncyclopadie der technischen Chemie, Vol. 16, 4th Edition, pages254-257, 1978). Trimer fatty acids are commercially available productswhich are obtained as residues in the distillation of dimer fatty acid,such as Pripol® 1040 of Unichema or Emery® 1000 of Emery.

In the context of the invention, low-melting additives of groups A) toF) are understood to be additives which can be converted into the liquidstate at temperatures below the decomposition temperatures mentionedabove and at normal pressure. Instead of intensive mixing, the cationiclayer compounds obtained after the production process may if desired besubsequently ground with one or more additives selected from groups A)to F) in the presence of polar organic solvents or water, preferably ingrinding mills and, more particularly, in a ball mill, dried andoptionally post-dried. In the context of the invention, polar organicsolvents are understood to be hydrocarbon compounds containing at leastone substituent more electronegative than carbon which are liquid atroom temperature (15 to 25° C.). Corresponding hydrocarbon compoundsinclude chlorinated hydrocarbons, alcohols, ketones, esters, ethersand/or glycol ethers. Suitable polar organic solvents are methanol,ethanol, n-butanol, acetone, methyl ethyl ketone, methyl isobutylketone, cyclohexanol, isophorone, ethyl acetate, lactic acid ethylester, 2-methoxyethyl acetate, tetrahydrofuran, ethylene glycolmonomethyl ether, diethylene glycol monoethyl ether. For this subsequentmodification, i.e. modification after drying of the cationic layercompounds produced in accordance with the invention to form a powder,the organic additives may be used in quantities of about 5 to about 100%by weight, based on the cationic layer compound.

The use of the additives A) to F) in connection with cationic layercompounds is known from WO 92/06135, WO 92/20732 and WO 92/20619.

The cationic layer lattice compounds produced in accordance with theinvention may be used as sole stabilizers for halogen-containingthermoplastic resins. However, they are preferably used in combinationwith other stabilizers. Besides the metal soaps already mentioned,suitable co-stabilizers are, above all, 1,3-diketone compounds, organicesters of phosphorous acid, polyols and amino acids.

Examples of 1,3-diketone compounds are: dibenzoyl methane, stearoylbenzoyl methane, palmitoyl benzoyl methane, myristoyl benzyl methane,lauroyl benzoyl methane, benzoyl acetone, acetyl acetone, tribenzoylmethane, diacetyl acetobenzene, p-methoxy and stearoyl acetophenone,acetoacetic ester.

Examples of suitable esters of phosphorous acid are triaryl phosphites,such as triphenyl phosphite, tris-(p-nonylphenyl)-phosphite (TNPP);alkylaryl phosphites, such as monoalkyl diphenyl phosphites, for examplediphenyl isooctyl phosphite, diphenyl isodecyl phosphite and dialkylmonophenyl phosphites, such as phenyl diisooctyl phosphite, phenyldiisodecyl phosphite, and trialkyl phosphites, such as triisooctylphosphite and tristearyl phosphite.

Examples of suitable polyols are trimethylol propane,di(trimethylolpropane), erythritol, pentaerythritol, dipentaerythritol,sorbitol, mannitol.

Examples of amino acid derivatives are glycine, alanine, lysine,tryptophane, acetyl methionine, pyrrolidonecarboxylic acid,β-aminocrotonic acid, α-aminoacrylic acid, α-aminoadipic acid and estersderived therefrom. The alcohol components of these esters includemonohydric alcohols, such as methanol, ethanol, propanol, isopropanol,butanol, 2-ethyl hexanol, octanol, iso-octanol, lauryl alcohol, stearylalcohol, and polyols, such as ethylene glycol, propylene glycol,1,3-butanediol, 1,4-butanediol, glycerol, diglycerol,trimethylolpropane, pentaerythritol, dipentaerythritol, sorbitol andmannitol.

Examples of suitable epoxy compounds are epoxidized soybean oil,epoxidized rapeseed oil, epoxidized esters of unsaturated fatty acids,such as epoxymethyl oleate, epoxybutyl oleate, epoxidized alicyclicsubstances, glycidyl ethers, such as bisphenol A diglycidyl ether,bisphenol F diglycidyl ether, glycidyl esters, such as glycidyl acrylateand glycidyl methacrylate.

The following Examples are intended to illustrate the invention withoutlimiting it in any way.

EXAMPLES

A) Production of the Cationic Laver Compounds

Example 1

Materials

Solution A

10.128 kg AlCl₃.6H₂ O (42.0 moles), 10.212 kg MgCl₂.6H₂ O (50.4 moles)and 1.680 kg ZnCl₂ (12.0 moles) are dissolved in 42 l of deionized waterwith gentle heating (volume of the solution: ca. 56 l).

Suspension B

4.452 kg of Na₂ CO₃ (42.0 moles) are dissolved in 21 l of deionizedwater and 20.04 kg of 50% NaOH (249.6 moles) are added to the resultingsolution. Addition of the NaOH resulted in partial precipitation (volumeof the suspension: ca. 36 l).

Method

Solution A was added to suspension B over a period of 30 to 45 minuteswith continuous stirring (800 to 1,100 r.p.m./blade stirrer). The crudeproduct precipitated as the viscosity increased, accompanied by a slightincrease in temperature. It was filtered off in vacuo by means of a blueband filter and washed with 36 l of water. The filter cake was taken upin 84 l of a 4-molar aqueous NaOH (obtained from 17.6 l of 50% aqueousNaOH and 66.4 l of deionized water) and crystallized for 16 h withstirring at 80° C. (three-necked flask with condenser; stirrer rotatingat 300 r.p.m.). The product was then filtered in vacuo by means of ablue band filter and thoroughly washed with water. Adhering water wasthen removed from the product in a vacuum drying cabinet at 110° C. 5.2kg of dry product were obtained.

B) Performance tests

The substance of Example 1 produced in accordance with the invention wastested for color stability at elevated temperature in accordance withDIN 5033. The test was carried out at 180° C. using sheeted-outcompounds as the test specimens. It was found that the long-term colorstability of the test specimens containing the product produced inaccordance with Example 1 as stabilizer was better than the long-termstability of corresponding test specimens containing commercialstabilizers, for example of the Alcamizer type (type 4, a product ofKyowa). Blackening of the test specimens only occurred after a testduration of 180 minutes (for comparison: the test specimen containingAlcamizer 4 turned black after only 150 minutes).

The following test formulation was used for the tests according to DIN5033:

    ______________________________________                                        PVC (Solvic 268; Solvay)                                                                             100.0  parts                                             Ca stearate 0.5 part                                                          Zn stearate 0.5 part                                                          Rhodiastab 50 (Rhoone Poulenc) 0.2 part                                       Test substance.sup.a) 1.0 part                                              ______________________________________                                         a)Invention: substance of Example 1                                           Comparison: Alcamizer 4                                                  

The test specimens were produced by homogenizing and plasticizing thePVC and the additives mentioned for 5 mins. at 170° C. on laboratorymixing rolls. 15 mm wide test strips were cut out from the ca. 0.5 mmthick sheets obtained and were treated in a thermo-oven at 180° C. Thetest strips were removed from the oven at 15-minute intervals untilblackening was observed.

What is claimed is:
 1. A process for preparing a modified cationic layercompound, said process comprising: subjecting a starting compound of thegeneral formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

to alkali-induced ripening in an aqueous medium for a period of from 2.5to 50 nours at a temperature of from 60° C. to 100° C., wherein theaqueous medium has an alkali metal hydroxide molar concentration of from1 to 6, wherein E represents at least one monovalent alkali metalcation, e represents a number of from 0 to 2, Z represents at least onedivalent metal cation, z represents a number of from 0 to 6, Drepresents at least one trivalent metal cation, d represents a number offrom 0 to 3, V represents at least one tetravalent metal cation, vrepresents a number of from 0 to 1, (A^(n-)) represents an acid anionhaving a charge n-, and wherein n represents an integer of from 1 to 3,q represents a number of from 1 to 10, x is greater than a, ande+2z+3d+4v=x+na.
 2. The process according to claim 1 wherein v has thevalue zero.
 3. The process according to claim 1 wherein e has the valuezero.
 4. The process according to claim 1 wherein v and e ha ve thevalue zero.
 5. The process according to claim 1 wherein e and v have thevalue zero, d has the value one, D stands for aluminum and x is a numberof 1 to
 5. 6. A process for stabilizing a halogen-containing plasticagainst thermal and/or photochemical degradation, said processcomprising:(a) providing a halogen-ontaining plastic composition; (b)providing a modified cationic layer compound; and (d) combining thehalogen-containing plastic composition and ine modified cationic layercompound;wherein the modified cationic layer compound is prepared bysubjecting a starting compound of the general formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

to alkali-induced ripening in an aqueous medium for a period of from 2.5to 50 hours at a temperature of from 60° C. to 100° C., wherein theaqueous medium has an alkali metal hydroxide molar concentration of from1 to 6, wherein E represents at least one monovalent alkali metalcation, e represents a number of from 0 to 2, Z represents at least onedivalent metal cation, z represents a number of from 0 to 6, Drepresents at least one trivalent metal cation, d represents a number offrom 0 to 3 V represents at least one tetravalent metal cation, vrepresents a number of from 0 to 1, (A^(n-)) represents an acid anionhaving a charge n-, and wherein n represents an integer of from 1 to 3,q represents a number of from 1 to 10, x is greater than a, ande+2z+3d+4v=x+na.
 7. The process according to claim 6 wherein v has thevalue zero.
 8. The process according to claim 6 wherein e has the valuezero.
 9. The process according to claim 6 wherein v and e have the valuezero.
 10. The process according to claim 6 wherein e and v have thevalue zero, d has the value one, D stands for aluminum and x is a numberof 1 to
 5. 11. The process according to claim 6, wherein saidhalogen-containing plastic composition comprises at least one polyvinylchloride selected from the group consisting of homopolymers andcopolymers.
 12. The process according to claim 6, further comprising:(c) providing a co-stabilizer selected from calcium and zinc salts ofcarboxylic acids containing 6 to 2 carbon atoms, wherein theco-stabilizer is combined with the halogen-containing plasticcomposition and the modified cationic layer compound.
 13. The processaccording to claim 6, wherein the modified cationic layer compound ispresent in an amount of from 0.01 to 5 parts by weight, based on theweight of the halogen-containing plastic compositions.
 14. A compositioncomprising a modified cationic layer compound prepared by subjecting astarting compound of the general formula (I):

    [E.sub.e Z.sub.z D.sub.d V.sub.v (OH.sup.-).sub.x ](A.sup.n-).sub.a.qH.sub.2 O                              (I)

to alkali-induced ripening in an aqueous medium for a period of from 2.5to 50 hours at a temperature of from 60° C. to 100° C. wherein theaqueous medium has an alkali metal hydroxide molar concentration of from1 to 6, wherein E represents at least one monovalent alkali metalcation, e represents a number of from 0 to 2, Z represents at least onedivalent metal cation, z represents a number of from 0 to 6, Drepresents at least one trivalent metal cation, d represents a number offrom 0 to 3, V represents at least one tetravalent metal cation, vrepresents a number of from 0 to 1, (A^(n-)) represents an acid anionhaving a charge n-, and wherein n represents an integer of from 1 to 3,q represents a number of from 1 to 10, x is greater than a, ande+2z+3d+4v=x+na.
 15. The composition according to claim 14, wherein vhas a value of zero.
 16. The composition according to claim 14, whereine has a value of zero.
 17. The composition according to claim 14,wherein V and e each have a value of zero.
 18. The composition accordingto claim 14, wherein v and e each have a value of zero, d has a value of1, D represent aluminum, and x has a value of from 1 to
 5. 19. Thecomposition according to claim 14, wherein the acid anion is selectedfrom the group consisting of carbonate, hydrogen carbonate, perchlorate,acetate, nitrate, tartrate, oxolate, and iodide.